Southeast and central Asia are witnessing rapid penetration by the global market economy. The urbanization that has paralleled this economic transformation has brought with it an increased spread of communicable diseases, often in areas with limited public health resources. Expansions in migrants' involvement in the urban-based informal labor sector is of particular concern because movement between urban centers and remote rural regions may serve as a mechanism for diffusing both behavioral risk practices as well as infectious diseases themselves. With a long history of social and economic marginalization, and increasing dependence on urban-based migrant labor, the Yi minorities are an especially vulnerable ethnic group in southern China. This socio-economic vulnerability may be exacerbated by the general lack of knowledge about transmission of HIV and STD's in the region. Developed as an exploratory pilot study using the R21 mechanism, this application proposes a targeted set of ethnographic methods with which to elaborate our understanding of how and why migrant labor may confer unique health risks, notably high risk for exposure to drug and sexual risk practices. We propose to focus on young adult Yi because our preliminary work suggests that many Yi become involved in migrant labor early in their adult lives and that exposure to drug and sexual risk also occur early. Since our pilot work suggests that gender is an important influence on the economic roles that men and women occupy in migrant labor, we propose to study both men and women. Based on an established ethnographic research design, the study will begin with a set of formative research activities that will serve to orient the research team in the local communities where the study will be conducted. Additionally, a small group of key participants will be recruited for a series of ethnographic interviews that will include questions about life history and life course events, family experience, education and skills acquisition, subsistence and income generating strategies, knowledge and beliefs about HIV/STD's, initiation of drug and sexual risk activities, and experiences of stigma (N=60). Interviews will yield information that will allow us to construct a preliminary epidemiological trajectory of how drug and sexual risk practices are initiated, and key features of the early course of behavioral risk, that would need to be anticipated in future research and prevention activities.